Sperm DNA damage in relation to lipid peroxidation following freezing-thawing of boar semen
This study investigated the relationships between lipid peroxidation (LPO) and sperm DNA damage following freezing-thawing of boar semen in different extenders. The comet assay was used to measure the extent of sperm DNA damage in a cryoprotectant-free extender or in cryoprotectant-based extenders after single and repeated freezing and thawing. As well as an analysis of sperm motion characteristics, mitochondrial function, membrane integrity, and lipid peroxidation (LPO) were assessed simultaneously with the measurements of sperm DNA damage. Consistent positive significant correlations were found between sperm DNA damage and LPO after freezing-thawing. Comet assay measurements showed that cryo-induced sperm DNA damage was more marked in the cryoprotectant-free extender, irrespective of freezing cycle. The frequency of sperm cells with damaged DNA increased with repeated freezing and thawing in the cryoprotectant-based extenders. Except for sperm DNA damage, there were no consistent associations between post-thaw sperm LPO and sperm quality characteristics. It could be suggested that the increased LPO of membrane phospholipids is associated with higher susceptibility of boar spermatozoa to cryo-induced DNA damage.
Keywords: Comet assay measurements, cryopreservation, extenders, spermatozoa